1. Field of the Invention
The present invention relates to a thermal activating device of a thermal activation sheet with a thermal activator layer for developing color and adhesion by heating formed on at least one surface thereof and a printer by using the thermal activating device, and more particularly to a technique of preventing a heat sensitive adhesive and a metamorphic material of the heat sensitive adhesive from attaching to the thermal activation sheet.
2. Description of the Related Art
Recently, as one kind of liner-less label, a thermal activation sheet (for example, heat sensitive adhesive label) is in a widespread use in various fields of, for example, a POS label of the foods, logistical and delivery label, label for medical care, baggage tag, display label for bottles and cans, and the like. The heat sensitive adhesive label is designed by forming a heat sensitive adhesive layer for developing the adhesion by heating, although it does not exhibit the adhesion at usual, on the back surface of a sheet-shaped label substrate (for example, base paper) and forming a printable surface on the front surface thereof. The heat sensitive adhesive mainly made from thermoplastic resin, solid elasticizer, and the like and it has a characteristic of developing the adhesion, activated through the heating by the thermal activating device, although it is non-adhesive at room temperature. Usually, the activation temperature is 50 to 150° C., and in this temperature range, a solid elasticizer within the heat sensitive adhesive is melted and the adhesion is added to the thermoplastic resin. Since the melted solid elasticizer is gradually crystallized after a supercooled state, the state of adhesion can last for predetermined hour and while maintaining this state of adhesion, the label is adhered to an object such as a glass bottle.
The printable surface of the heat sensitive adhesive label is formed by, for example, a heat sensitive coloring layer, and a desired letter, image and the like is printed on the printable surface by a thermal printer having a general thermal head, and after the printing, the heat sensitive adhesive layer is activated by the thermal activating device.
A printer is being developed in which the thermal activating device is installed in the thermal printer so as to continuously perform the thermal printing on a heat sensitive adhesive label and the activation of a heat sensitive adhesive layer.
This printer has the structure, for example, as illustrated in FIG. 11.
In FIG. 11, the reference mark P2 indicates a thermal printer unit, the reference mark C2 indicates a cutter unit, the reference mark A2 indicates a thermal activating unit, and the reference mark R indicates a heat sensitive adhesive label reeled like a roll.
The thermal printer unit P2 comprises a printing thermal head 100, a platen roller 101 which is pushed toward the printing thermal head 100, and a driving system (for example, a driving motor, a gear series, and the like), not illustrated, for rotating the platen roller 101. By rotating the platen roller 101 in the direction of D1 (clockwise) in FIG. 11, the heat sensitive adhesive label R is drawn out, and after printing in a thermal method on the heat sensitive adhesive label R drawn out, the label is forwarded in the direction of D2 (in the right direction). The platen roller 101 has pressing means (for example, a coil spring, a flat spring, and the like) not illustrated, and the elastic force is adopted to push the surface of the platen roller 101 to the thermal head 100, serving as the pressuring means of the heat sensitive adhesive label R. The heat sensitive adhesive label R has the structure, for example, as illustrated in FIG. 12. Namely, a thermal coat layer 501 as a heat sensitive coloring layer for forming the printable surface is provided on one surface of the base paper 500 (front surface in FIG. 12) as a label substrate, and on the above layer, a color printing layer 502, for example, with a frame of the price, characters of the unit and the like, pattern, and the like printed there, is formed. A thermal activator layer K, with the heat sensitive adhesive, mainly made from the thermoplastic resin, the solid elasticizer, and the like, applied thereto, is formed on the other surface of the base paper 500 (the back surface in FIG. 12).
The printer unit P2 of FIG. 11 can perform a desired printing on the thermal coat layer 501 of the heat sensitive adhesive label R by operating the printing thermal head 100 and the platen roller 101, according to a printing signal from a printing controller, not illustrated.
The function of the cutter unit C2 is to cut the heat sensitive adhesive label R that has been heat-sensitively printed by the thermal printer unit P2, by a proper length, and it is formed by a movable blade 200, a fixed blade 201, and the like operated by a driving source (not illustrated) of the electric motor and the like. The movable blade 200 is operated at a predetermined timing, according to a control of the controller, not illustrated.
The thermal activating unit A2 is provided with a loading roller 300 and a discharging roller 301 for inserting and discharging the cut heat sensitive adhesive label R, which are rotated, for example, by the driving source not illustrated, and a thermal head 400 for thermal activation and a platen roller 401 pushed toward the thermal head 400 for thermal activation are arranged between the loading roller 300 and the discharging roller 301. The platen roller 401 has a driving system (for example, an electric motor, a gear series, and the like) not illustrated, so as to rotate the platen roller 401 in the direction of D4 (clockwise direction in FIG. 11) and forward the heat sensitive adhesive label R in the direction of D6 (in the right direction in FIG. 11) by the loading roller 300 and the discharging roller 301 rotating respectively in the direction of D3 and in the direction of D5. Further, the platen roller 401 has the pressing means (for example, a coil spring, a flat spring, and the like) not illustrated, and this elastic force is adopted to push the surface of the platen roller 401 toward the thermal head 400 for thermal activation with the pressure F.
That one indicated by the reference mark S is a discharge detecting sensor for detecting the discharge of the heat sensitive adhesive label R. According to the detection of the discharge of the heat sensitive adhesive label R by the discharge detecting sensor S, the next heat sensitive adhesive label R is printed, forwarded, and activated. The thermal head 400 for thermal activation and the platen roller 401 are operated at a predetermined timing by a controller not illustrated, the thermal activator layer K of the heat sensitive adhesive label R is activated by the heat given by the thermal head 400 for thermal activation, thereby developing the adhesion.
After the adhesion of the heat sensitive adhesive label R has been developed by thus constituted thermal printer unit P2, the display label, the price tag, and the advertisement label are stuck to a glass bottle, a plastic bottle, and the like including alcohol, chemicals, and the like. Accordingly, since a separate sheet (liner) such as a conventional general adhesive label sheet is not necessary, it is effective in reducing the cost, and since any separate sheet that will become wastes after use is not required, there is a merit from a viewpoint of the environmental concerns and resource saving.
In the conventional thermal activating unit A2 of the heat sensitive adhesive label R, however, there is a problem such that a heat sensitive adhesive and a metamorphic material of the heat sensitive adhesive (chemically metamorphosed or carbonized material by heat) are attached to the forwarding means (especially, the platen roller 401) of the heat sensitive adhesive label R and the thermal head 400.
Namely, since the platen roller 401 is always in a state of being pushed toward the thermal head 400 by the pressure F, when the heat sensitive adhesive label R is removed from the platen roller 401 after a heater element H of the thermal head 400 for thermal activation has heated and activated the thermal activator layer K of the heat sensitive adhesive label R cut by the cutter unit C2 by a predetermined length, some of the heat sensitive adhesive of the thermal activator layer K is softened by the heating and squeezed out from the space between the platen roller 401 and the thermal head 400 for thermal activation by the pressure F, into a state of being separated from the base paper 500 of the heat sensitive adhesive label R, as illustrated in FIG. 13(a).
The heat sensitive adhesive label R is discharged, with the platen roller 401 once in an idle running state, and the heat sensitive adhesive G1 separated as shown in FIG. 13(a) comes into a state of sticking around the surface of the platen roller 401 by the adhesion generated by activation, as illustrated in FIG. 13(b).
By repeating the states as shown in FIGS. 13(a) and (b) several times, it turns into a state of sticking a lot of grained heat sensitive adhesives G1 to the surface of the platen roller 401, as illustrated in FIG. 13(c). There may occur the case where the stuck heat sensitive adhesives G1 are chemically metamorphosed or transformed into a carbonized material G2 by a lot of heating by the thermal head 400 for thermal activation, hence to be fixedly attached to the surface of the platen roller 401.
Since the heat sensitive adhesive G1 attached to the surface of the platen roller 401 has a stronger adhesion according to the melting through several times of heating by the thermal head 400 for thermal activation, there is a fear of attaching some to the surface of the forwarded heat sensitive adhesive label R and damaging the printing surface.
Further, a lot of attached heat sensitive adhesives G1 damage the smoothness on the surface of the platen roller 401 and thermal activator layer K of the heat sensitive adhesive label R being forwarded cannot be heated uniformly, which causes a situation incapable of bringing out a full adhesion disadvantageously.